This invention relates to slip-casting.
Slip-casting is a known technique for casting ceramic articles in which a finely ground ceramic in a liquid suspension, or slip, is poured into a porous mold which absorbs the liquid and leaves a layer of ceramic deposited on the mold walls. When the desired thickness of ceramic is obtained, the excess liquid is poured out. The deposited casting is allowed to dry before being removed for sintering. The conventional mold material is plaster.
The use of plaster molds for slip casting has a number of limitations. It is very difficult to obtain thin molded castings, or articles having a large contact area with the mold, without breaking or cracking. Also, many ceramics, such as .beta.-alumina, are difficult to remove from plaster molds since the castings tend to stick to the mold walls, even with the use of additives such as glycerine or sodium alginate. Moreover, the use of additives to facilitate demolding adversely affects the purity and porosity of the article. Also, casting in plaster molds is time-consuming, the molds must be dried between castings, and must be replaced after about five castings since the pores become clogged.